5. Normalisation

What are controlled redundancies?

Controlled redundancies are redundancies that are allowed for the convenience of structuring data, data manipulation or reporting.

Describe Partial functional dependency

Partial functional dependency occurs when a column is functionally dependent on a composite primary key.

What are the effects of implementing Normalisation?

1) Eliminating non-atomic values 2) Reducing data redundancies 3) Avoiding data anomalies 4) Producing a set of controlled redundancies 5)Forming and organizing tables that have proper structures and clearly defined data relationship

Name the Database Design Errors?

1) Modification/Update Anomaly (Changes to existing data are not correctly recorded. Due to multiple records with the same data attributes.) 2) Insert/Addition Anomaly (Unable to add a record to the database) 3) Delete Anomaly (Removing a record also removes unintended data from the database.)

What is a Key Attribute?

A key attribute is an attribute that is part of at least one key candidate. All other attributes are non-key attributes

What is a key candidate?

A key candidate is a key with a minimum number of a attributes

What is 1NF?

A) No data field contains multiple values from the column's domain (atomic values) B) Each row is unique (a unique primary key exists)

What is 2NF?

A) The table is in 1NF. B) Does not contain any partial functional dependencies

What is 3NF?

A) The table is in 2NF. B) Does not contain any transitive functional dependencies

What is Normalisation?

Normalisation looks at the bottom-up view. Normalisation: a set of rules and a process of assigning attributes to entities to eliminate repeating groups and data redundancies, and to form tables representing entities that promote structural and data independence.

Describe Transitive functional dependency

Transitive functional dependency occurs when nonkey columns functionally determine other nonkey columns of a relation